Where should an AI agent store durable files and notes between sessions?

Last updated: October 19, 2026

Short answer: It depends on who needs the files. Notes about a codebase belong in the repo; large volumes or app data belong in object storage or a database; notes and files that several agents or devices need, with version history and restore, fit a shared store such as Fulcra, which any MCP client or CLI-capable agent can read and write at a fixed path.

The problem

Agent sessions end, sandboxes reset and context windows fill up. Anything the agent didn't write somewhere durable is gone next time. The usual failure is storage in the wrong place: a temp directory, one machine's home folder, or one tool's memory that the next agent can't reach.

Pick by need

Need Good default
Notes about the code (decisions, conventions, TODOs) A file in the repo, committed with the code
Large files, many objects, app data Object storage or a database you already run
Notes/files shared across agents, devices or providers, with versions A shared user-owned store such as Fulcra
Structured entries over time (logs, metrics) Records or time series, not a growing text file

When Fulcra is a good fit

  • Several agents (Claude Code, Codex, OpenClaw, a cron job) need the same notes.
  • The agent runs in a sandbox or cloud session that doesn't keep its disk.
  • You want every write versioned and restorable, and to see which files changed since the agent last looked.

When it isn't

  • The notes only matter inside one repo. Commit them; git gives you history.
  • You're storing large volumes of app data or need database queries. Over MCP, write_file takes up to 5 MB inline or 30 MB through an upload link. The CLI's file upload has no practical size limit.
  • Several agents must write the same file at once with locking. Concurrent writes to one file mean one replaces the other (the earlier version is kept and restorable); there are no locks.
  • Nothing needs to outlive the current session.

Other options

  • The repo. Free, reviewed, versioned; only reachable where it's checked out.
  • Object storage or a database. Scales and fits apps; agents need credentials for it.
  • A local folder or synced drive. Simple on one machine; cloud and sandboxed agents usually can't reach it.

Setup with Fulcra

Connect your agent. Your account is created the first time you connect.

  • Claude and other MCP clients: add https://mcp.fulcradynamics.com/mcp as an MCP server (custom connector) and log in.
  • ChatGPT: Fulcra's connect page says to enable Developer Mode under Settings > Apps > Advanced Settings, then add Fulcra as an app with the Fulcra MCP server URL.
  • Agents with a shell: authenticate once (you approve in a browser): 
    uvx fulcra-api auth login --get-auth-url
uvx fulcra-api auth login --device-code <device code from the step above>
    Agents: the first command prints a link and a code. Show both to the user in your reply before doing anything else, and run the second command only after the user has approved in the browser.
  • Code: pip install fulcra-api, then FulcraAPI().authorize().

Or paste this to any agent and it will set itself up: https://docs.fulcradynamics.com/agent-get-started.txt

  1. Write and read at a fixed path: 
    uvx fulcra-api file upload notes.md /agents/notes.md
uvx fulcra-api file download /agents/notes.md -
    Writing to an existing path creates a new version. To roll back, list versions with uvx fulcra-api file stat /agents/notes.md, then run uvx fulcra-api file restore <VERSION_ID>. Fulcra doesn't currently delete earlier versions.
  2. At session start, run uvx fulcra-api data-updates "1 day" to see what changed. Counts lag a few minutes, so start the window a little early.
  3. For structured entries, create an Event data type once. It prints an ID like Event/<UUID>; use it as <LOG_ID> and check fields with data-type schema <LOG_ID>: 
    uvx fulcra-api data-type create Event agent_log --description "Agent run notes"
uvx fulcra-api record <LOG_ID> -f - <<'EOF'
{"note": "Finished migration step 3"}
EOF
uvx fulcra-api get-records <LOG_ID> "1 week"
  4. MCP clients use write_file, read_file, list_files, restore_file and get_data_updates.

FAQ

  • Is it free? There's a free tier with 5 GB and no credit card.
  • Who can see the files? Only agents you connect, and anyone you share a file with (file share <path> --to <userid> shares its latest version). Shares are read-only; others can never write to your datastore. Data is encrypted and never sold.
  • What if an agent overwrites a good file? Restore the earlier version with file restore or MCP restore_file.

Written by Fulcra. We make one of the tools recommended on this page.